Prime Minister Julia Gillard will today announce that she is calling a ballot to resolve the Labor leadership stoush with her predecessor Kevin Rudd.

Ms Gillard will hold a morning press conference in Adelaide to call a caucus ballot for Monday, when Parliament resumes.

Overnight she criticised Mr Rudd over his sudden resignation as Foreign Minister, saying she was "disappointed" he did not speak to her before his announcement.

"I am disappointed that the concerns Mr Rudd has publicly expressed this evening were never personally raised with me, nor did he contact me to discuss his resignation prior to his decision," she said in a statement.

This morning Attorney-General Nicola Roxon told ABC News Breakfast that a leadership spill was inevitable, and predicted an easy win for Ms Gillard.

I am disappointed that the concerns Mr Rudd has publicly expressed were never personally raised with me, nor did he contact me to discuss his resignation prior to his decision.

"The party has given Kevin Rudd all the opportunities in the world and he wasted them with his dysfunctional decision-making and his deeply demeaning attitude towards other people, including our caucus colleagues," he said in a statement.

"He sought to tear down the 2010 campaign, deliberately risking an Abbott prime ministership, and now he undermines the Government at every turn.

"He was the party's biggest beneficiary then its biggest critic, but never a loyal or selfless example of its values and objectives."

Mr Rudd resigned in Washington at a snap press conference called in the middle of the night.

He said he would not be part of the leadership "soap opera" and that resigning was the only "honourable" thing for him to do.